A number of photographic processes by which images may be developed and viewed within seconds or minutes after exposure have been proposed. Such processes generally employ a processing composition which is suitably distributed between two sheet-like elements, the desired image being carried by one of said sheet-like elements. The resulting images may be in black-and-white, e.g., in silver, or in one or more colors. Processing may be conducted in or outside of a camera. The most useful of such processes are the diffusion transfer processes which have been proposed for forming silver or dye images, and several of these processes have been commercialized. Such processes have in common the feature that the final image is a function of the formation of an imagewise distribution of an image-providing reagent and the diffusion transfer of said distribution to or from the stratum carrying the final image, whether positive or negative. It has also been proposed to form the final desired image in the photosensitive stratum per se by monobath processing to obtain a negative image or by so-called direct position processing to obtain a positive image, employing processing techniques and physical film structures similar to those found useful in diffusion transfer processing.
The copending applications of Edwin H. Land, Ser. No. 786,352, filed Dec. 23, 1968 and now abandoned; Ser. No. 43,782, filedJune 5, 1970 and now abandoned; and Ser. No. 101,968, filed Dec. 28, 1970 and now abandoned, as a continuation-in-part of the first mentioned Ser. No. 786,352 now U.S. Pat. No. 3,647,437 relate to such photographic processes wherein development may be performed, at least in part, outside of a camera, i.e., in light actinic to the photosensitive layer or layers. These applications disclose systems wherein an organic light-absorbing material or reagent, preferably a dye, is included in the processing composition so as to preclude fogging by actinic light incident thereon, i.e., from that side of the film unit when the exposed film unit is processed in the light. The resulting "opaque" processing composition cooperates with opacifying means on the other side of the exposed photosensitive element, e.g., an opaque support layer, and means for precluding edge light leakage, so that, after application of the processing fluid, the film unit may be developed in the light.
The organic light-absorbing material may comprise a dye, sometimes referred to as an "indicator dye" which is highly colored within a first pH range but which is substantially transparent at a second pH range so as to permit viewing of the resulting photographic image. In one such embodiment, this light-absorbing dye may be highly colored at the pH of an aqueous alkaline processing composition, e.g., 13-14, but will be substantially non-absorbing of visible light at a lower pH, e.g., less than 10-12. This pH reduction may be effected by an acid-reacting reagent appropriately positioned in the film unit, e.g., a polymeric acid layer. The processing composition may, if necessary, contain a mixture of such light-absorbing materials so as to obtain light absorption in all critical areas of the visible and non-visible by which the photosensitive strata, e.g., a panchromatic black-and-white silver halide emulsion or a multiclor silver halide photosensitive element being used are exposable.
Suitable light-absorbing dyes of this description are disclosed in the aforementioned copending applications as well as in the following patents: U.S. Pat. No. 3,702,245; U.S. Pat. No. 3,833,615; U.S. Pat. No. 3,833,614; U.S. Pat. No. 3,702,244 and U.S. Pat. No. 3,772,329. Illustrative light-absorbing dyes will be detailed hereinafter.
Processing compositions including at least one light-absorbing organic material, e.g., the aforementioned indicator dyes, may be employed in various photographic systems, as is disclosed with greatest particularity in the aforementioned application Ser. No. 101,968. These photographic systems include systems for preparing reflection prints or transparencies, positive or negative, in black-and-white or in color. Color systems which may be employed include the various known additive or subtractive color systems, e.g., diffusion transfer, dye bleach, color processes employing an additive color screen, etc. Particularly useful photographic systems for forming visible images are those employing diffusion transfer techniques to provide an imagewise distribution of image-providing material which is transferred, by diffusion, to an image-receiving layer to impart thereto the desired photographic image. Illustrative diffusion transfer systems will be described hereinafter.
Common to all of these photographic systems contemplated by the present invention is the concept of forming the desired image by applying to the exposed film unit a processing composition including one or more organic light-absorbing materials such that the film unit may be protected from fogging by light incident on the thus applied processing composition during the development process.
Preferred processing compositions contemplated by this invention are those containing, in addition to the light-absorber, an inorganic light-reflecting agent providing the requisite background so that the resulting photographic image may be viewed by reflected light.
As was mentioned previously, particularly useful systems contemplated by this invention for forming photographic images are the various diffusion transfer systems for forming color images which have heretofore been disclosed in the art. Generally speaking, such systems rely for color image formation upon a differential in mobility or solubility of a dye image-providing material obtained as a function of development so as to provide an imagewise distribution of such material which is more diffusible and which is therefore selectively transferred, at least in part, by diffusion, to a superposed dyeable stratum to impart thereto the desired color transfer image. The differential in mobility or solubility may for example be obtained by a chemical action such as a redox reaction or a coupling reaction.
The dye image-providing materials which may be employed in such processes generally may be characterized as either (1) initially soluble or diffusible in the processing composition but are selectively rendered non-diffusible in an imagewise pattern as a function of development; or (2) initially insoluble or non-diffusible in the processing composition but which are selectively rendered diffusible in an imagewise pattern as a function of development. These materials may be complete dyes or dye intermediates, e.g., color couplers.
As examples of initially soluble or diffusible materials and their application in color diffusion transfer, mention may be made of those disclosed, for example, in U.S. Pat. Nos. 2,647,049; 2,661,293; 2,698,244; 2,698,798; 2,802,735; 2,774,668; and 2,983,606. As examples of initially non-diffusible materials and their use in color transfer systems, mention may be made of the materials and systems disclosed in U.S. Pat. Nos. 3,443,939; 3,443,940; 3,227,550; 3,227,551; 3,227,552; 3,227,554; 3,243,294 and 3,445,228.
In any of these systems, multicolor images are obtained by employing a film unit containing at least two selectively sensitized silver halide layers each having associated therewith a dye image-providing material exhibiting desired spectral absorption characteristics. The most commonly employed elements of this type are the so-called tripack structures employing a blue-, a green- and a red-sensitive silver halide layer having associated therewith, respectively, a yellow, a magenta and a cyan dye image-providing material.
A particularly useful system for forming color images by diffusion transfer is that described in U.S. Pat. No. 2,983,606, employing dye developers (dyes which are also silver halide developing agents) as the dye image-providing materials. In such systems, a photosensitive element comprising at least one silver halide layer having a dye developer associated therewith (in the same or in an adjacent layer) is developed by applying an aqueous alkaline processing composition. Exposed and developable silver halide is developed by the dye developer which in turn becomes oxidized to provide an oxidation product which is appreciably less diffusible than the unreacted dye developer, thereby providing an imagewise distribution of diffusible dye developer in terms of unexposed areas of the silver halide layer, which imagewise distribution is then transferred, at least in part, by diffusion, to a dyeable stratum to impart thereto a positive dye transfer image. Multicolor images may be obtained with a photosensitive element having two or more selectively sensitized silver halide layers and associated dye developers, a tripack structure of the type described above and in various patents including the aforementioned U.S. Pat. No. 2,983,606 being especially suitable for accurate color recordation of the original subject matter.
In color diffusion transfer systems of the foregoing description, color images are obtained by exposing a photosensitive element or "negative component" comprising at least a light-sensitive layer, e.g., a gelatino silver halide emulsion layer, having a dye image-providing material associated therewith in the same or in an adjacent layer, to form a developable image; developing this exposed element with a processing composition to form an imagewise distribution of a soluble and diffusible image-providing material; and transferring this imagewise distribution, at least in part, by diffusion, to a superposed receiving element or "positive component" comprising at least a dyeable stratum to impart to this stratum a color transfer image. The negative and positive components may be separate elements which are brought together during processing and thereafter either retained together as the final print or separated following image formation; or they may together comprise a unitary structure, e.g., integral negative-positive film units wherein the negative and positive components are laminated and/or otherwise physically retained together at least prior to image formation.
Of particular interest are those integral negative-positive film units adapted for forming color transfer images viewable without separation, i.e., wherein the positive component containing the dye transfer image need not be separated from the negative component for viewing purposes. In addition to the aforementioned essential layers, such film units further include means for providing a reflecting layer between the dyeable stratum and the negative component in order to mask effectively the silver image or images formed as a function of development of the silver halide layer or layers and any remaining associated dye image-providing material and to provide a background for viewing the color image formed in the dyeable stratum, without separation, by reflected light. This reflecting layer may comprise a preformed layer of a reflecting agent included in the essential layers of the film unit or the reflecting agent may be provided after photoexposure, e.g., by including the reflecting agent in the processing composition. These essential layers are preferably contained on a transparent dimensionally stable layer or support member positioned closest to the dyeable stratum so that the resulting transfer image is viewable through this transparent layer. Most preferably another dimensionally stable layer which may be transparent or opaque is positioned on the opposed surface of the essential layers so that the aforementioned essential layers are sandwiched or confined between a pair of dimensionally stable layers or support members, at least one of each is transparent to permit viewing therethrough of a color transfer image obtained as a function of development of the exposed film unit in accordance with the known color diffusion transfer system such as will be detailed hereinafter. In a particularly preferred form such film units are employed in conjunction with a rupturable container of known description containing the requisite processing composition and adapted upon application of pressure of applying its contents to develop the exposed film unit, e.g., by applying the processing composition in a substantially uniform layer between the dyeable stratum and the negative component. It will be appreciated that the film unit may optionally contain other layers performing specific desired functions, e.g., spacer layers, pH-reducing layers, etc.
Opacifying means may be provided on either side of the negative component so that the film unit may be processed in the light to provide the desired color transfer image. In a particularly useful embodiment such opacifying means comprise an opaque dimensionally stable layer or support member positioned on the free or outer surface of the negative component, i.e., on the surface of the film unit opposed from the positive component containing the dyeable stratum to prevent photoexposure by actinic light incident thereon from this side of the film unit and an opacifying agent applied during development between the dyeable stratum and the negative component, e.g., by including the opacifying agent in a developing composition so applied, in order to prevent further exposure (fogging) by actinic light incident thereon from the other side of the film unit when the thus exposed film unit is developed in the light. The last-mentioned opacifying agent may comprise the aforementioned reflecting agent which masks the negative component and provides the requisite background for viewing the transfer image formed thereover. Where this reflecting agent does not by itself provide the requisite opacity it may be employed in combination with an additional opacifying agent in order to prevent further exposure of the light-sensitive silver halide layer or layers by actinic light incident thereon.
As examples of such integral negative-positive film units for preparing color transfer images viewable without separation as reflection prints, mention may be made of those described and claimed in U.S. Pat. Nos. 3,415,644, 3,415,645, 3,415,646 and 3,473,925, 3,573,043, 3,573,044, 3,672,890, 3,594,165 and 3,594,164.
In general, the film units of the foregoing description, e.g., those described in the aforementioned patents and/or copending applications, are exposed to form a developable image and thereafter developed by applying the appropriate processing composition to develop exposed silver halide and to form, as a function of development, an imagewise distribution of diffusible dye image-providing material which is transferred, at least in part by diffusion, to the dyeable stratum to impart thereto the desired color transfer image, e.g., a positive color transfer image. Common to all of these systems is the provision of a reflecting layer between the dyeable stratum and the photosensitive strata to mask effectively the latter and to provide a background for viewing the color image contained in the dyeable stratum, whereby this image is viewable without separation, from the other layers or elements of the film unit. In certain of these systems, this reflecting layer is provided prior to photo-exposure, e.g., as a preformed layer included in the essential layers of the laminar structure comprising the film unit, and in others it is provided at some time thereafter, e.g., by including a suitable light-reflecting agent, for example, a white pigment such as titanium dioxide, in the processing composition which is applied between the dyeable stratum and the next adjacent layer to develop the latent image and to form the color transfer image.
The dye image-providing materials which may be employed in such processes generally are selected from those materials heretofore mentioned and disclosed in the illustrative patents which were initially soluble or diffusible in the processing composition but which are selectively rendered non-diffusible as a function of development or those which are initially insoluble or non-diffusible in the processing composition but are selectively rendered diffusible as a function of development. These materials may be complete dyes or dye intermediates, e.g., color couplers.
These film units may, and usually do, further contain pH modulating or adjusting means, e.g., a layer or layers containing a reagent for adjusting the pH following substantial transfer image formation. In those systems employing an aqueous alkaline processing composition, such film units may contain a neutralizing layer or layers, e.g., a polymeric acid layer of the type described, for example, in U.S. Pat. No. 3,362,819. It is also known to employ a spacer layer in conjunction with the neutralizing layer in order to "time" control the pH adjustment by the neutralizing layer. Spacer layers of this description are disclosed, for example, in the aforementioned U.S. Pat. No. 3,362,819, as well as in other patents, e.g., U.S. Pat. Nos. 3,455,686; 3,433,633; 3,421,893; 3,419,389; etc. The neutralizing and spacer layers are preferably contained in the positive component, e.g., as layers disposed on the side of the dyeable stratum opposed from the negative component. However, they may be disposed in the negative component, as is described and claimed in U.S. Pat. No. 3,573,043.
Preferred positive components employed in film units of the foregoing description comprise a transparent support or dimensionally stable layer carrying an acid neutralizing layer, a timing or spacer layer and a dyeable stratum or image-receiving layer. The positive component may also contain additional layers performing specific desired functions.
A preferred opacification system to permit development in the light is that described in the aforementioned copending application of Edwin H. Land, Ser. No. 43,782 -- now abandoned -- which employs a processing composition including an inorganic reflecting pigment dispersion containing at least one optical filter agent at a pH above the pKa of the optical filter agent in a concentration effective, when the processing composition is applied, to provide a layer exhibiting optical transmission density &gt; than about 6.0 density units with respect to incident radiation actinic to the photosensitive silver halide layer and optical reflection density &lt; than about 1.0 density with respect to incident visible radiation.
In lieu of having the reflecting pigment contained in the processing composition, e.g., as disclosed in the aforementioned copending application Ser. No. 43,782 -- now abandoned -- the reflecting pigment needed to mask the photosensitive strata and to provide the requisite background for viewing the color transfer image formed in the receiving layer may be contained initially in whole or in part as a preformed layer in the film unit. As an example of such a preformed layer, mention may be made of that disclosed on the copending applications of Edwin H. Land, Ser. Nos. 846,441, filed July 31, 1965 now U.S. Pat. No. 3,615,421 and 3,645, filed Jan. 19, 1970 now U.S. Pat. No. 3,620,724. The reflecting pigment may be generated in situ as is disclosed in the copending applications of Edwin H. Land, Ser. Nos. 43,741 and 43,742, both filed June 5, 1970 and now U.S. Pat. Nos. 3,647,434 and 3,647,435 respectively.